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Subject: Re: [PATCH] tracing, perf : add cpu hotplug trace events
From: Steven Rostedt <rostedt@goodmis.org>
To: Amit Kucheria <amit.kucheria@linaro.org>
Cc: Vincent Guittot <vincent.guittot@linaro.org>, linux-kernel@vger.kernel.org,
        linux-hotplug@vger.kernel.org, fweisbec@gmail.com
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Date: Fri, 07 Jan 2011 10:52:08 -0500
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On Fri, 2011-01-07 at 14:51 +0530, Amit Kucheria wrote:

> > +
> > +TRACE_EVENT(hotplug_start,
> > +
> > + TP_PROTO(unsigned int type, unsigned int step, unsigned int cpuid),
> > +
> > + TP_ARGS(type, step, cpuid),
> > +
> > + TP_STRUCT__entry(
> > + __field(u32, type)
> > + __field(u32, step)
> > + __field(u32, cpuid)
> > + ),
> > +
> > + TP_fast_assign(
> > + __entry->type = type;
> > + __entry->step = step;
> > + __entry->cpuid = cpuid;
> > + ),
> > +
> > + TP_printk("type=%lu step=%lu cpuid=%lu", (unsigned long)__entry->type,
> > + (unsigned long)__entry->step, (unsigned long)__entry->cpuid)
> > +);
> > +
> > +TRACE_EVENT(hotplug_end,
> > +
> > + TP_PROTO(unsigned int type, unsigned int step, unsigned int cpuid),
> > +
> > + TP_ARGS(type, step, cpuid),
> > +
> > + TP_STRUCT__entry(
> > + __field(u32, type)
> > + __field(u32, step)
> > + __field(u32, cpuid)
> > + ),
> > +
> > + TP_fast_assign(
> > + __entry->type = type;
> > + __entry->step = step;
> > + __entry->cpuid = cpuid;
> > + ),
> > +
> > + TP_printk("type=%lu step=%lu cpuid=%lu", (unsigned long)__entry->type,
> > + (unsigned long)__entry->step, (unsigned long)__entry->cpuid)
> > +);
> > +
> > 

Please use classes when having tracepoints that have the same fields.
This will save a bit of kernel memory. Something like:


DECLARE_EVENT_CLASS(hotplug_template,

	TP_PROTO(unsigned int type, unsigned int step, unsigned int cpuid),

	TP_ARGS(type, step, cpuid),

	TP_STRUCT__entry(
		__field(u32, type)
		__field(u32, step)
		__field(u32, cpuid)
	),

	 TP_fast_assign(
		__entry->type = type;
		__entry->step = step;
		__entry->cpuid = cpuid;
	),

	TP_printk("type=%lu step=%lu cpuid=%lu", (unsigned long)__entry->type,
		(unsigned long)__entry->step, (unsigned long)__entry->cpuid)
);

DEFINE_EVENT(hotplug_template, hotplug_start,
	TP_PROTO(unsigned int type, unsigned int step, unsigned int cpuid),
	TP_ARGS(type, step, cpuid);

DEFINE_EVENT(hotplug_template, hotplug_end,
	TP_PROTO(unsigned int type, unsigned int step, unsigned int cpuid),
	TP_ARGS(type, step, cpuid);

-- Steve